HO-102 Annual and Perennial Flowers · 2019-08-22 · mous range of ornamental herbaceous plants....

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University of KentuckyCollege of Agriculture,Food and EnvironmentCooperative Extension Service

Can you imagine a world without flowers? Their textures, col-ors, scents, and forms inspire gardeners, artists, and writers. The desire to grow flowers often motivates novices to take

up gardening and moves experienced gardeners to become flower specialists. Annuals, biennials, and herbaceous perennials offer variety and interest to all styles of gardens.

Not so long ago, flowers often were separated from other parts of the garden. Masses of colorful annuals filled park and home dis-play beds only in summer. Herbaceous perennials, laid out in long borders, demanded intense management without providing year-round interest. Since the 1980s, however, American garden design had moved away from flower displays that are attractive for only a few months, and gardeners now plan landscapes for all seasons. In today’s smaller gardens, often entirely visible from inside the home, combinations of evergreen and deciduous shrubs, conifers, and perennial flowers keep the scene fascinating year-round. Gardens often include spring-flowering bulbs, containers of annual flowers, herbs for cooking or tea, and grasses for winter texture.

Plants in contemporary gardens are selected not only for their flowers, but for multiseason characteristics, such as leaf form, foli-age texture, and color. Flowers remain important, but the gardening world is taking advantage of new possibilities offered by an enor-mous range of ornamental herbaceous plants. These include annu-als, biennials, perennials, and bulbs.

Types of Herbaceous Ornamental PlantsAnnuals

Annuals live briefly. They germinate, grow, bloom, and go to seed in one year. Because they die at the end of this cycle, they must be replanted the following season.

Many annuals come up on their own from the previous year’s seeds. Some, such as California poppies (Eschscholzia californica) and bachelor’s buttons (Centaurea cyanus), can become weedy by reappearing from seed so prolifically. Whether or not this char-acteristic is desirable depends on your garden’s style. Informally designed cottage-style gardens gain from self-seeded plants, but formal gardens, which require precise balance and layout, do not, and volunteer annuals must be removed.

Annual and Perennial FlowersKentucky Master Gardener Manual Chapter 13By Mary Robson, retired extension agent, King and Pierce counties, Washington State University. Adapted for Kentucky by Sharon Bale, floriculture extension specialist and Rick Durham, consumer horticulture extension specialist and master gardener state coordinator.

HO-102

In this chapter:Types of Herbaceous Ornamental Plants .177

Using Herbaceous Perennials in Garden Design ...................................................................179

Flower Garden Maintenance .........................184

Bulbs, Corms, Rhizomes, Tubers, and Tuberous Roots ..................................................186

Specialized Herbaceous Flower Gardens..188

For More Information .......................................189

CHaPTeR 13178 • Annual and Perennial Flowers

Colorful, long-blooming, and easy to grow, annuals offer much to gardens. They often produce flowers or decorative leaves steadily from early summer until they set seed or are killed by frost. Annuals are particularly useful for colorful window boxes, container plantings, hanging baskets, and school or youth gardens. Their quick growth from seeds or transplants is gratify-ing for young gardeners.

Some cool-season annuals such as pan-sies (Viola wittrockiana) and ornamental kale (Brassica spp.) can be planted in fall to replace summer annuals in containers, window boxes, and gardens. Table 1 lists the heightand bloom color of common annuals.

BiennialsBiennials often confuse gardeners. They

require two full years to complete their growth cycle and die after the second year. The first year, they grow foliage and roots but do not flower. The second year, they flower and go to seed. Their garden uses are closer to those of annuals than perenni-als, but many are cherished components of perennial gardens.

Some biennials are spectacularly showy because the inflorescence (flower stalk) can be huge, as on the gray-leafed Verbascum olympicum, which reaches 8 or 9 feet tall. Foxgloves (Digitalis purpurea), forget-me-nots (Mysotis sylvatica), and hollyhocks (Alcea rosea) are common biennials.

Provide undisturbed space for biennial plants, because they require a summer growing season and winter rest before flow-ering. Many biennials need winter protec-tion in cold climates. Some gardeners start biennials in a nursery bed and move them to permanent positions in their second year when they are ready to flower.

Know how to identify the first-year leaves (the vegetative stage) to avoid pulling the plants as weeds before their second-year flowering period.

In some cases, newer cultivars of some biennials have been bred to produce blooms the first season. Hollyhock ‘Queeny Purple’ and digitalis ‘Camelot’ are just two examples. When choosing a plant, be sure to read the information about that particu-lar cultivar.

PerennialsUnlike annuals and biennials, perennial

plants live year after year. Trees and shrubs are woody perennials. Mature garden, park, and arboretum landscapes often are com-posed mostly of woody perennial plants.

Many familiar garden flowers are peren-nials, such as peonies (Paeonia spp.) and Shasta daisies (Leucathemum maximum).

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Table 1. Height and bloom color of common annuals.

PlantHeight

(inches) Bloom colorafrican daisy 6 - 12 White, yellow, salmonageratum 4 - 24 Blue, whiteamaranthus 48 - 96 Red, red and greenarctotis 24 White with bluish eyeaster (Callistephus chinensis) 18 Yellow, pinkish red, blue,

white, lavenderbacopa 6-10 White, blueBalsam (Impatiens balsamina) 12 - 18 Rose, purple, whiteBasil, purple (foliage) 15 Red-purple foliageBegonia 6-12 Pink, red, whiteBrowallia 8 - 12 Blue, violet, whiteCalendula 12 - 24 Yellow, gold, orangeCabbage, flowering 8 - 14 Red to whiteCalilbrachoa 6-12 VariousCastor bean (foliage) 72 - 96 Red, inconspicuous flowersCapsicum 6-24 Red, orange, purple fruitCockscomb (Celosia) 18 - 36 Blue, red, yellow, orangeCornflower (Centaurea cyanus) 36 Pink, blue, whiteColeus (foliage) 8 - 20 Variegated foliageCosmos sulphureus 18 - 24 Red, orange, yellowCosmos bipinnatus 48+ White, lavenderDusty miller (Artemisia stellerana) 24 Silvery foliage, yellow flowersevolvulus ‘Blue Daze’ 6-10 BlueFan flower (Scaevola aemula) 6-8 Blue, whiteForget-me-not (Myosotis) 12 Blue, pinkFour o’clock (Mirabilis) 24 Pink, white, yellowGaillardia pulchella 15 - 24 Yellow, orange, redGeranium 12-18 pink, red, white, salmon,

lavender

CHaPTeR 13 Annual and Perennial Flowers • 179

These plants are called herbaceous because they do not form permanent woody branch structures as do shrubs and trees.

Hardy perennials live through winter in the ground, reviving from their crowns in spring. They send up new shoots, often through the remains of the previous year’s dead stems, leaves, and flowers. Some perennials, such as peonies (Paeonia spp.), may survive for decades, long outliving the gardener who planted them. Some may only live a few years in the garden, if at alll. It is very important to choose perennials that are appropriate for the location’s hardi-ness zone and general climate conditions.

Some hardy perennials may live for several years in this area and then mysteriously die when no obvious disease or insect prob-lem is apparent. This type of death is often attributed to the “weather.” When we have wide temperature fluctuations during the winter, the hardiness of the plant may be affected.

Tender perennials won’t survive outdoor winter conditions even with protection. They must be lifted before frost, stored, and replanted after danger of freezing weather passes. Dahlias, gladiolus, and tuberous begonias, are just some examples.

How a perennial is classified depends on the climate zone the plant is being grown in. For example, a lantana in an annual in Kentucky. In southern Florida it has become an invasive perennial. When purchasing perennials look for those plants that are hardy in Zone 6 or less. Some parts of Kentucky are Zone 7 but plants that are labeled as Zone 7b may have some hardi-ness problems.

Using Herbaceous Perennials in Garden Design

Because perennials reappear year after year, they have advantages over annuals. The plants can fill space rapidly if grown in proper conditions. Many reach their mature size several years after planting, expand-ing gradually into large, showy clumps. There are hundreds of different perennials, each with a distinct texture, color, scent, and form, which makes choosing plants an intriguing adventure.

Most perennials bloom for a fairly short time, from one to three weeks, although some, such as coreopsis (Coreopsis verticil-lata), can bloom persistently for as long as six weeks. Careful perennial plant selec-tion can provide garden interest from early spring to frost and even through winter.

Table 1. Height and bloom color of common annuals.

PlantHeight

(inches) Bloom colorGomphrena 12 - 36 Lavender, purple, red, whiteHeliotrope 10 RoseImpatiens 8 - 24 Red, pink, white, orangeLantana 12-36 Red, yellow, white, lavenderLicorice plant 6-10 Grey, lime-greenLobelia 4 - 18 Blue, violet, white, pinkMandevilla Vine PinkMarigold (Tagetes) 8 - 48 Yellow, orange to red-brownMelampodium 24 YellowMimulus 12 - 30 Yellow, redNicotiana 24 - 48 Red, pink, whiteNigella 12 - 15 White, blue, violetPansy (Viola) 8 - 12 Blue, purple, white, yellowPetunia 6 - 12 White to rose, purplePortulaca 8 Yellow, white, rose, orangeSalvia 18 - 36 Blue, red, whiteSalvia farinacea (Mealycup sage) 14-18 Blue, whiteSnapdragon (Antirrhinum) 6 - 18 Blue, purple, yellow, orange,

redStatice, (Limonium) sinuatum 18 - 24 Yellow, rose, violet, whiteStrawflower (Helichrysum) 36 White, red, yellowSunflower (Helianthus) 12 - 108 Yellow to red-brownSweet alyssum (Alyssum maritimum)

3 - 10 White, purple

Sweet Potato vine vine Green, purpleTithonia 48 OrangeTorenia 12 White, blue, violetVerbena 8 - 24 White, pink, blue, redVinca 8-12 White, lavender, pinkZinnia 6 - 36 Red, pink, yellow, orange,

white, lime green


Italian arum (Arum italicum) is an exam-ple of a plant that produces winter interest. The foliage appears in late fall and persists over the winter. The bright orange-red ber-ries that are produced on strong stems also provide color well into the winter.

Successful flower gardening depends, as does any other aspect of gardening, on understanding your site’s character-istics and matching them to the needs of individual plants. Annual and perennial flowers have been hybridized for centu-ries, chosen from wild plants originating in bogs, sunny prairies, alpine meadows, woodland shade, and many other grow-ing conditions. Understand your garden environment before selecting herbaceous plants. Analyze the hours of daylight, soil texture, drainage, water availability, and winter frost conditions. Choose plants that have cultural needs matching your garden’s characteristics.

For a low-maintenance perennial garden, consider several basic plant characteristics: • Is the plant long-lived (lasting at least

four seasons)? • Does it grow strongly but not overwhelm

other plants? • Will it have a long bloom time? • Is it attractive when out of bloom? • Is it generally pest-resistant?

Peonies (Paeonia spp.), purple cone-flower (Echinacea purpurea), and Autumn Joy sedum (Sedum spectabile ‘Autumn Joy’) are among the many herbaceous perennials that meet these criteria.

Garden design (which should be based on harmonious color patterns), bloom throughout the seasons, and intriguing year-round texture depend on the gar-dener’s taste. Because herbaceous plants are used intensively in modern gardens, many books have excellent suggestions on how to design with them. Visiting gardens and nurseries and keeping an idea notebook also will help you develop design confi-dence and improve your garden choices. continued on next page

Table 2. Bloom season, height, and bloom color of common perennials.*

Botanical name Common nameHeight

(inches) Color

Late winter, springChionodoxa luciliae glory-of-the-snow 4 blueCrocus (species and hybrids)

crocus 4 various

Endymion hisipanicus Spanish bluebell 12-15 blue, whiteEranthis hyemalis winter aconite 3 yellowGalanthus nivalis common snowdrop 6-12 whiteHelleborus (species and hybrids)

Lenten rose 15-18 various

Hyacinthus orientalis hyacinth 12-14 variousIberis sempervirens candytuft 3-6 whiteIris danfordiae danford iris 4-6 yellowLeucojum vernum spring snowflake 10-12 whiteMertensia virginica Virginia bluebells 12-14 blueMuscari armeniacum grape hyacinth 6-8 blueNarcissus pseudonarcissus narcissus, daffodil varies variousScilla siberica Siberian squill 3-6 blueTulipa (species and hybrids)

tulip varies various

Late spring, early summerAchillea filipendulina fern-leaf yarrow 24-36 yellowAmsonia tabernaemontana amsonia 12-36 blueAquilegia (hybrids) columbine varies variousAurinia saxatilis basket-of-gold 12 yellowArmeria maritima common thrift 6-12 pinkAstilbe arendsii astilbe 24-36 variousBaptisia australis false indigo 36-48 blueBrunnera macrophylla heartleaf brummera 12-18 blueCampanula glomerata clustered bellflower 12-18 blue,

purpleConvallaria majalis lily of the valley 10-12 white, pinkDianthus barbatus sweet William 10-18 variousDianthus gratianapolitanus cheddar pink 9-12 rose, pinkDicentra spectabilis common bleeding heart 18-24 pinkGalium odoratum sweet woodruff 4-9 whiteHeucherella tiaraelloides foamy bells 15-24 pinkHemerocallis (hybrids) daylily varies variousIris (hybrids) tall bearded iris 12-24 variousIris sibirica Siberian iris 24-36 variousLeucanthemum x superbum shasta daisy 18-24 whitePaeonia suffructicosa tree peony varies variousPaeonia (hybrids) peony varies variousPapaver orientale Oriental poppy 18-36 variousPhlox subulata moss phlox 6-9 various


Table 2 lists perennials by season of bloom and gives their height and bloom color. Figure 1 illustrates how plants can be arranged according to height, while Figure 2 shows arrangement by season of bloom. Figure 3 is an example of a garden design that combines perennial and annual flowers with a variety of bloom seasons, colors, heights, and textures.

Selecting PlantsSelect annual and perennial plants for

the best possible growth qualities. The popularity of flower gardening encour-ages plant hybridizers and growers to offer improved plants with more vigor, larger flowers, longer bloom periods, and more attractive leaves. For instance, pansies have been selected for color and form, produc-tion of pink flowers, orange/purple com-binations (Viola wittrockiana ‘Jolly Joker’), and diminutive yellow forms as well as the familiar, large, purple-whiskered faces.

When a design specifies a particular plant, look for cultivars that may have improved characteristics over the parent plant. Often this means seeking a named variety rather than simply a straight species. Association garden sales, specialty nurser-ies, mail-order catalogs, and knowledge-able local gardeners are good sources for extraordinary plants.

Table 2. Bloom season, height, and bloom color of common perennials.*

Botanical name Common nameHeight

(inches) Color

SummerAchillea millefolium common yarrow 12-18 variousAsclepias tuberosa butterfly weed 24-36 orangeCoreopsis grandiflora tickseed 12-24 yellowCoreopsis verticillata thread leaf coreopsis 18-36 yellowEchinacea purpurea purple coneflower 24-36 purple,

variousEchinops ritro globe thistle 12-36 blueHeliopsis helianthoides sunflower heliopsis 36-48 yellow,

orangeHeuchera sanguinea coral bells 12-18 redHosta (species, hybrids) hosta 6-36 purple,

whiteLiatris spicata spike gayfeather 24-36 mauveLimonium latifolium sea lavender 24-30 lavenderIris kaempferi Japanese iris 34-30 variousLilium (species, hybrids) lily varies variousPerovskia atriplicifolia Russian sage 48+ bluePhlox paniculata garden phlox 36-48 variousRudbeckia fulgida orange coneflower 18-30 yellow

Late summer and early fallAnemone x hybrida Japanese anemone 24-36 white, pinkAster novae-angliae New england aster 48+ violet,

purpleAster novi-belgii Michaelmas daisy 12-48+ violetEupatorium purpureum Joe-Pye weed 48+ purpleSedum spectabile showy stonecrop 12-24 pinkTricyrtis hirta common toad-lily 24-36 lilac

*Bloom times are only an estimate because location and spring temperatures can cause plants to bloom earlier or later than expected.

Figure 1. Flower border divided into bold plant groupings according to height. Background: large groups of tall plants. Foreground: shallower, wider groupings of small plants.

Figure 2. Flower border designed for continuous bloom from spring through fall.


Spread 3 to 4 inches of organic material across the soil surface and dig it in well. This addition will help increase the soil’s water-holding capacity and improve root penetration and aeration. Commercial compost, homemade compost, chopped or composted leaves, composted sawdust, fine bark, and composted manure make good amendments.

Recognize that many perennials form large, heavy root structures, which can rot if the site isn’t well-drained, particularly if there is a high water table in winter. If you face this situation, improve drainage or choose plants suitable for damp condi-tions (for instance, cardinal flower [Lobelia cardinalis]).

Soil testing is helpful when starting a gar-den on an unfamiliar site or when expand-ing an existing garden. Many herbaceous perennials grow well in slightly acid soil, but some need supplemental lime if the soil pH is below 6.0. A soil test will provide a recommendation for adjusting the pH if it is required. Generally, sulphur can be added to lower the pH and lime can be added to increase the pH.

PropagationAnnuals and biennials

These flowers generally are started from seed or are purchased as small plants. Many annual seeds can be sown directly in the garden. For annuals that are hard to trans-plant, such as Shirley poppies (Papaver rhoeas), direct seeding is necessary. When choosing flowers for children’s gardens, seeds such as nasturtiums (Tropaeolum majus) and sunflowers (Helianthus annuus), which sprout quickly and are large enough to handle, inspire satisfaction.

Many other annuals and biennials do best if started in a propagation bed or tray and then transplanted as small plants. Marigolds (Tagetes spp.), violas and pansies (Viola spp.), and snapdragons (Antirrhinum majus) transplant well. Start seedlings indoors four to six weeks before they will be

Soil PreparationIf you follow some sensible basic steps

when installing a new garden, you’ll have good results. For perennial gardens, soil preparation is a key to strong future growth. Later applications of fertilizer can’t com-pensate for poorly prepared soil.

First, get rid of weeds, especially perenni-als such as quackgrass, dandelions, morning glory, and thistles. Then dig thoroughly, loosening the soil to at least 12 inches. (Double-digging often is recommended for herbaceous perennial gardens. This pro-cess involves digging 20 to 24 inches deep, loosening the soil, and moving the top layer down about one shovel’s depth. This prac-tice increases air and nutrients available to roots and can produce a fine garden site capable of sustaining plants for many years.)

Figure 3. Sample perennial/annual bed with a mix of bloom seasons, flower colors, and heights. In spring, blocks 1, 2, 3, 4, and 5 will bloom. In summer, blocks 4, 6, 7, 8, 9, 10, 11, and 12 will bloom. a=annual; P=Perennial.

1. Tulip (P): spring; color varies; 8–24"2. Da�odil (P): spring; shades of white or yellow; 8–24"3. Hyacinth (P): spring; pink, white, purple; 8–12"4. Pansy (A, late winter planting): winter, spring; blue,

purple, white, yellow; 8–12"; Ageratum (A, June planting after pansy is �nished): summer; blue, white; 4–24"

5. Candytuft (P): spring; white; 12"6. Dwarf marigold (A): summer; yellow, orange to

red-brown; 8–12"7. Zinnia (A): summer; red, pink, yellow, orange,

white; 6–36"8. Dusty miller (P): summer; silvery foliage, yellow

�owers; 24"9. Salvia (A): summer; blue, red, white; 18–36"10. Cockscomb (A): summer; blue, red, yellow, orange;

18–36"11. Larkspur (A): spring, summer; blue, pink,

white; 18–36"12. Globe amaranth (A): summer; white, pink, purple;

15–30"


planted in the garden. Provide ample light, using auxiliary light if necessary, to grow stocky, healthy transplants. Beware of start-ing seedlings too early; they grow poorly if left too long in low light and crowded indoor conditions.

Buying seedlings from nurseries is very convenient, especially for annuals with very fine seeds, notably petunias, impatiens, and fibrous begonias. Unless you have excellent propagation facilities, plants are difficult to grow from fine seed.

Perennials Perennials grow more slowly than annu-

als, and many do not bloom the first year, although some will. You can start them from seed in a nursery bed and transplant them to a final location when they are sturdy enough. Often they are ready to transplant late in their first season.

Keep in mind that starting perennials from seed can be a slow process and may require waiting several years before any blooms appear. The cost of purchasing perennials is often directly related to the number of years the plant has been in pro-duction. While some of the newer cultivars of certain perennials have been bred to produce blooms the first season from seed-ing, others require several years of growth before any blooms will be produced.

Division—As herbaceous perennials develop established root systems, they spread into large clumps, so many can be propagated by division.

Divide perennials as part of your general garden maintenance, because growth and performance decrease when plants get crowded. Centers die out on many plants, such as Siberian iris (Iris siberica). Division rejuvenates plants and results in extra plants to share with friends or donate to plant sales.

The proper time to divide perennials depends on the particular plant. In general divide fall-blooming plants such as aster (Aster spp.) in very early spring. Spring bloomers such as iris (Iris spp.) can be divided in late summer or early fall.

Select vigorous shoots from the outer part of a clump. Discard the center. Divide the plant into several sections of three to five shoots each. Make large divisions, because small pieces will not bloom much the first year after planting. Before replant-ing, add compost or other organic materials to the soil.

Cuttings—Many plants can be propagated from either tip or root cuttings. Generally, tip cuttings are easier to grow than root cuttings.

Take 2- to 6-inch-long tip cuttings from perennials such as candytuft (Iberis sem-pervirens) or lavender (Lavandula angus-tifolia and others). Remove all foliage from the lower one-third of the cutting. Insert cuttings in a clean planting mix such as one-half sharp sand and one-half peat moss.

Professional growers supply bottom heat and provide moisture through automatic misting systems that keep cuttings moist while roots form. If you don’t have these systems, rooting will be slower and require more care, but you still can be successful. Cover cuttings with a sheet of clear plastic to retain moisture. Support the plastic to keep it from touching the foliage. Place the cuttings in a light area but out of direct sun. In direct sun, high temperatures can build up under the plastic on warm days and can kill cuttings.

When cuttings resist a slight tug, they have begun to root. The plants then start to take up water and nutrients. Poke holes in the plastic to provide more air circulation to the rooting plants, gradually adding holes as more roots grow. When the plants have formed good root balls, transplant them to a nursery bed or container and begin fertilizing.


Root cuttings also work to propa-gate some plants, such as Oriental pop-pies (Papaver orientalis), phlox (Phlox paniculata), and baby’s breath (Gypsophila paniculata). Dig plants in late summer after they have bloomed and are going dormant. Choose pencil-sized roots and cut them into 4-inch sections. Shoots will not appear until the following growing season.

Flower Garden MaintenanceRegular, planned maintenance keeps

plants healthy and a garden looking attractive.

FertilizingAnnuals need regular fertilizing. Well-

prepared soil and organic mulch help make nutrients available to plants, but annuals grow so rapidly that supplemental fertilizer helps. When planting, incorporate about 5 pounds per 100 square feet of 5-10-5 or 5-10-10 fertilizer. Then fertilize at regular intervals, about every three weeks. Don’t add fertilizer to dry soil; be sure to water before and after fertilizing.

When planting a new perennial garden, add about 5 pounds of 5-10-5 or 5-10-10 per 100 square feet and dig it in thoroughly before planting. Fertilize established herba-ceous perennials as they start growth each year. Perennial plants that bloom in late summer or fall, such as asters, need regular fertilization before bloom, so feed them monthly until September. Perennials such as peonies that complete their bloom and growth by June do not need fertilizer in mid-summer. In general, two light applications of fertilizer per year are sufficient for supplying extra nutrients if soil conditions are good. Always water after applying fertilizer.

WeedingKeep annuals and perennials free of

weeds. A combination of hand weeding and mulch is effective. Weed regularly to prevent seeds from becoming established. Herbaceous plants shade out some weeds when mature but require extra vigilance while they are too small to compete.

Use herbicides with great care in herba-ceous plantings, if at all. Always read the label of any herbicide before using. The label will list plants that will not be damaged as well as list those plants that may be severely damaged by that particular chemical. Use them only around woody plants established in the landscape for more than six months.

It’s best to remove annual weeds at the seedling stage by hoeing lightly, avoiding the roots of desired plants. You can spot-treat persistent perennial weeds such as morningglory with a postemergent herbi-cide such as glyphosate (sold as Roundup and many other trade names), but take great care to keep herbicides off the leaves of all desirable plants.

WateringMost annuals need regular water

because they don’t make deep root systems. However, some annuals, such as cosmos (Cosmos bipinnatus), tolerate summer dry spells.

Do not allow herbaceous perennials to dry out in their first season. Many tolerate dry soils once established, however. Interest in water conservation causes many garden-ers to choose plants that need little supple-mental water. Plants such as artemisia, echinacea, Jerusalem sage (Phlomis spp.), and santolina use only moderate amounts of water.

To use water efficiently, group plants according to water needs. Till the soil deeply and amend it with compost or other organic material.

When you water, use efficient methods such as soaker hoses or drip irrigation sys-tems, and apply water slowly and deeply.


MulchingOrganic mulch is useful in perennial and

annual flower beds. Use compost (commer-cial or homemade), composted sawdust, chopped or composted leaves, or other materials for mulching.

Two applications of mulch each year are helpful. Apply 2 to 3 inches in spring after weeding and fertilizing to retain soil moisture, suppress annual weed seeds, and improve the bed’s appearance. Apply mulch again in late fall. As it breaks down over winter, this material will provide some winter protection and weed suppression.

Do not cover a perennial plant’s crown (the central growing area above the roots) with winter mulch, but do bring it up to the edge of the crown. In cold locations, you can cover the entire plant after the soil freezes or after several freezing nights. If you cover plants too soon, they may begin to grow under the mulch and may be killed by severe cold. Evergreen boughs make a good mulch, particularly in cold winter areas.

Pull mulch off plants in early spring when weather warms, allowing new growth to emerge.

StakingMany tall herbaceous flowering plants

must be tied to stakes or provided with another support system, especially in windy and exposed areas. Dahlias, for example, may require support. Wind, rain, or the weight of foliage and blossoms will bend or

Figure 4. Staking plants: In (a) and (b), plants are tied too tightly. In (c) and (d), principal branches loosely. which is better.

(a) (b) (c) (d)

break these plants’ stems and ruin the dis-play. Broken stems also can lead to disease problems.

Many short perennials such as peo-nies require support to keep flower heads upright. A plant that flops over onto adjoin-ing plants will smother its neighbors and destroy a garden’s attractiveness.

Commercial systems such as grates with legs work fine, but you also can improvise supports from bamboo stakes, twigs, or branches. Choose staking material that is about 6 inches shorter than the plants’ ultimate height.

Whatever method you use, put support systems in place while plants are small and tie plants loosely to the stake as they grow (Figure 4). Rapid growth will hide the stake, wires, or strings.

Deadheading and Disbudding Regular maintenance for annuals

includes removing flowers before they go to seed. This process is called deadheading. By preventing seed formation, you can extend the bloom period on many plants, such as pansies, marigolds, and petunias.

Deadheading not only might prolong the bloom period, but it improves a gar-den’s appearance. Some early summer-blooming perennials such as certain daylilies (Hemerocallis spp.) produce a second flush of flowers in fall if stems are cut to the ground after bloom and before seeds set. In other cases, however, seeds may be part of the gar-den show. Gladwin iris (Iris foeditissima), for example, is grown for its showy seed pods.


Plants such as dahlias produce larger flowers if disbudded. A stalk may have five or six buds; to disbud, snap off all but one on each stem.

Fall Cleanup Late fall maintenance generally includes

cutting back dead stems of herbaceous perennials and pulling out annuals after they are killed by frost. Some gardeners leave seed heads for birds. Goldfinches love cosmos seeds, and chickadees eat sunflower seeds right off the plants if squirrels don’t get them first. The seeds of many perennials, such as purple coneflower (Echinacea pur-purea), attract birds in late summer and fall.

Pest ManagementAll flower gardens eventually have some

pests or diseases. Learn to use the principles of integrated pest management and concen-trate on growing healthy plants. Strong plants resist disease and insect problems better than weak ones. To reduce disease infestations and cut down on hiding places for insects and other pests such as slugs, space plants properly to allow good air circulation, clean up litter and dead leaves, and control weeds.

Several diseases commonly affect annu-als, bulbs, and herbaceous perennials. Powdery mildew (a fungus) attacks peonies, zinnias, roses, pansies, and many other flowering plants, producing a gray, fuzzy coating on leaves and blossoms. Tulips, lilies, and peonies contract botrytis, which affects buds and stems and destroys flower-ing. Pruning out diseased plant parts can help control this disease.

Whenever possible, choose disease-resis-tant cultivars. Check with nurseries for new cultivars of phlox and bee balm (Monarda) with powdery mildew resistance.

Some insects damage a wide variety of plants. For example, aphids suck juices from many flowering plants. Learn the life cycles of garden pests so that you can protect ben-eficial predators and minimize use of broad-spectrum insecticides. Aphids, for example, have many natural enemies, including lady beetles, lacewings, wasps, and birds.

Slugs and snails attack tender shoots of bulbs, lilies, and young transplants and are often a problem where hostas are planted. Hand picking and selective use of baits can help you manage slugs. Place baits in traps rather than broadcasting them.

Consult relevant publications and experts for specific controls. Make sure you have properly identified the problem before applying any control.

Bulbs, Corms, Rhizomes, Tubers, and Tuberous Roots

Many garden plants are classified botanically as bulbs, corms, rhizomes, tubers, or tuberous roots. All of these have underground organs that store food for the plant. Many, such as hyacinths, tulips, and crocuses, can survive for a time without soil around their roots, which enables them to be stored and shipped easily. Figure 5 illustrates flowers of several types of bulbs and corms.

Bulbs are composed of a thin, flattened stem surrounded by fleshy, dried leaf bases called scales. Roots grow from a basal plate. Onions, garlic, narcissus, tulips, and lilies are examples of plants that form bulbs. Slicing an onion vertically and observing the interior gives a good look at a bulb’s anatomy.

Corms have solid interiors, developed from swollen stems. If you cut one, you see a homogenous mass inside. Roots form at the base. Some examples of plants that form corms are crocus, watsonia, and gladiolus.

Tubers are swollen, modified, under-ground stems. They don’t have basal plates where the roots originate. Tubers come in various shapes and include caladium.

Tuberous roots are composed of root tissue. Dahlias and tuberous begonias are examples of plants with tuberous roots.

Rhizomes are specialized stems that grow horizontally at or just below the soil surface. German iris, lily-of-the-valley, and bamboo have rhizomes.


Figure 5. Bulbs and corms offer a variety of blossoms.

36

Hei

ght (

inch

es)

30

24

18

12

6

5” 8”

Planting depth

very early spring early spring mid-spring late spring

Bloom time

Galanthus (Snowdrop)Eranthis (Winter aconite)

Anemone blandaIris reticulata

CrocusGrape hyacinth

HyacinthTulip (early)

Da�odilsTulips

(midseason)

Fritillariaimperialis

Tulip (late)

Alliumgiganteum

Gardeners often lump these different botanical structures under one heading, call-ing them all “bulbs.” This loose classification works for general purposes, but the distinc-tions between the types make a difference in how each is propagated and stored.

Like other herbaceous ornamentals, bulbs, corms, and tubers are classified as hardy or tender. Most hardy bulbs and corms are planted in fall for early spring bloom. Crocuses, narcissus, tulips, hya-cinths, and grape hyacinths define spring for many people. Lilies, which bloom in early or midsummer, may be planted in fall or early spring.

Tender bulbs, tubers, and corms gener-ally bloom in mid-to-late summer. Examples are dahlias, tuberous begonias, and gladiolus. Plant them when the ground warms after the last frost. To keep these plants for more than one season, dig them up in the fall and store them in a frost free location.

Selection and StorageChoose solid, healthy plants. With lil-

ies, tulips, and narcissus, larger bulbs yield larger blossoms. Some bargain bulbs are not worth the price, no matter how inexpensive, because they are too small to bloom well.

Purchase hardy bulbs in the fall. Don’t leave bulbs in a hot car trunk while shop-ping; the plants may be damaged or killed. If you can’t plant bulbs immediately, keep them cool and dry. Temperatures below 65°F are best for storage. Use paper sacks rather than plastic bags, since mold may develop if moisture accumulates inside the package.

After digging plants such as dahlias and cannas in the fall, store them in slightly damp peat or perlite. Do not let them com-pletely dry out; check them regularly and dampen them if necessary.


Fertilize spring bloomers when they are about an inch tall, using a 5-10-10 granular formula or a liquid fertilizer. In dry areas, water spring-blooming bulbs after flower-ing ends. Let the leaves wither naturally and don’t pull them out until they are brown. Move spring-blooming bulbs and corms only after all foliage has ripened (usually in late summer).

Specialized Herbaceous Flower Gardens

Specialized herbaceous flower gardens include container plantings, bog gardens, and water gardens.

Container Plantings Almost all gardeners have some form

of container plantings, often in addition to other types of gardens. Containers allow even those with limited space such as a rooftop, balcony, or front stoop to have vigorous gardens.

The potting material contributes vitally to the success of container plants. Plant roots must get sufficient air. If the soil is too dense, it packs down, contributing to root rot or other difficulties. Be sure to use a pot-ting material that contains sufficient gritty particles in the form of pumice, perlite, or vermiculite. Garden soil doesn’t work well in containers because watering packs it and reduces available oxygen.

Choose a container suited to the plant’s eventual size, and be sure it has sufficient drainage holes in the bottom. Scrub pots well. Do not add a layer of gravel or other material to the bottom of the pot; this prac-tice actually reduces drainage. Fill the clean pot full of potting soil.

You can reuse potting mixes year after year unless the plants in them were seri-ously diseased. Before replanting, dump the mix out of the pot, aerate it, and add new grit if necessary.

Annuals grown in containers will require more frequent fertilization. Regular water-ing will leach the initially applied nutrients from the soil. Follow the package directions

Site Preparation and PlantingDrainage is vital for most bulbs, corms,

tubers, rhizomes, and tuberous roots. With a few exceptions, such as Japanese iris (Iris ensata), they rot in wet soil. Snowdrops (Galanthus nivalis), crocuses, narcissus, tulips, and lilies must have excellent drain-age. If your garden site drains poorly, place bulbs in containers or raised beds.

Dig the soil as for annual or perennial flowers and add organic amendments such as compost. Remove all perennial weeds before planting, and watch for emerging annual weed seedlings after planting.

When planting, excavate the planting area, place fertilizer below the root level, and mix it thoroughly with soil. Slow-release fertilizers or general 5-10-10 formu-lations work well for fall-planted bulbs. Do not place bulbs directly on fertilizer.

Don’t plant bulbs and tubers in dry soil; roots cannot begin to grow without mois-ture. If the soil is very dry during fall plant-ing, dig a hole for the bulbs, fill it with water, and allow it to drain before planting.

Planting depth depends on soil condi-tions. Kentucky extension publications or local nurseries can give you specific sugges-tions. Many growers suggest planting about three times the depth of the bulb.

Shallow-planted bulbs may frost-heave and are easily dug out by rodents, which munch on them. To prevent rodent dam-age, plant them in a hardware cloth “cage.”

Mulch hardy bulb and corm plantings lightly with 2 to 4 inches of composted leaves, shredded fir bark, or composted sawdust. Keep mulches open and light enough to allow shoots to emerge in spring.

Watering and FertilizingAfter planting, be sure to water the

planting bed thoroughly and continue to water during periods of dry weather in the fall. Fall-planted bulbs begin to produce a root system and lack of water may severely damage the bulbs.


for slow release fertilizers. An additional. application may be necessary mid way though the growing season. If water soluble fertilizers are being applied follow the label recommendations for how frequently this should be applied. Remember, plants grown in containers will require regular water-ing. When watering plants be sure to water thoroughly and then allow the plants to dry out before watering again. Smaller contain-ers such as hanging baskets may require watering twice a day to maintain vigor during the heat of the summer. Generally, the larger the container the less frequently it will need to be watered.

Bog and Water GardensSmall fountains, pools, and other water

features are increasingly popular in gardens. Many herbaceous perennials adapt well to water gardening. A pool can be surrounded with Japanese iris (Iris ensata), ligularia (Ligularia dentata), rodgersia (Rodgersia podophylla), and adapted native plants. A barrel with a fountain bubbler can hold water lilies, many of which are winter-hardy, even in cold climates.

Some gardeners place a simple, shal-low bowl of water in the garden to reflect the sky. Water features also attract wildlife, especially birds.

For More InformationUK Extension PublicationsHO-65, Annual FlowersHO-76, Perennials for Sunny LocationsHO-77, Perennials for Shady LocationsHO-80, Spring, Summer, and Fall Bulbs

BooksArmitage, A.M., Armitage’s Manual of

Annuals, Biennials, and Half-Hardy Perennials (Timber Press, Portland OR, 2001).

Armitage, A.M., Armitage’s Garden Annuals (Timber Press, Portland OR, 2004)

Armitage, A.M. Herbaceous Perennial Plants: A Treatise on Their Identification, Culture, and Garden Attributes, 3rd ed. (Stipes Pub Lic., 2008).

Bloom, A. Alan Bloom’s Hardy Perennials (Batsford, London, 1991).

Eyewitness Garden Handbooks: Perennials, 1st American ed. (DK Publishing, New York, 1996).

Elliott, J. The Smaller Perennials (Timber Press, Portland, OR, 1997).

Hansen, R., and F. Stahl. Perennials and Their Garden Habitats, 4th ed. (Timber Press, Portland, OR, 1993).

Harper, P. Designing with Perennials (Macmillan, New York, 1990).

Harper, P., and F. McGourty. Perennials: How to Select, Grow, and Enjoy (HP Books, Tucson, 1985).

Hartmann, H.T. Plant Propagation: Principles and Practices, 7th ed. (Prentice Hall, Englewood Cliffs, NJ, 2001).

Hobhouse, P. Color in Your Garden (Little, Brown, and Co., New York, 1985).

Lloyd, C., and G. Rice. Garden Flowers from Seed (Timber Press, Portland, OR, 1994).

Macunovich, J. Caring for Perennials: What to Do and When to Do It (Storey Publishing, Pownal, VT, 1997).

Phillips, R., and M. Rix. The Random House Book of Perennials, 2 vols. (Random House, New York, 1991).

Raven, S. The Cutting Garden: Growing and Arranging Garden Flowers (Frances Lincoln, Pleasantville, NY, 2006).

Rix, M. Growing Bulbs (Timber Press, Portland, OR, 1986).

Thomas, G.S. Perennial Garden Plants or the Modern Florilegium, 3rd ed., revised (Sagapress, with Timber Press, Portland, OR, 1990).

Wilson, J.W. Landscaping with Container Plants (Houghton Mifflin, Boston, 1990).

PeriodicalsFine Gardening www.finegardening.comGarden Design www.gardendesign.comGardens Illustrated www.gardensillustrated.

comHorticulture www.hortmag.com


educational programs of Kentucky Cooperative extension serve all people regardless of economic or social status and will not discriminate on the basis of race, color, eth-nic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expression, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability. Issued in furtherance of Cooperative extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Depart-ment of agriculture, M. Scott Smith, Director of Cooperative extension Programs, University of Kentucky College of agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 2012 for materials developed by University of Kentucky Cooperative extension. This publication may be reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at www.ca.uky.edu.Issued 3-2012

HO-102 Annual and Perennial Flowers · 2019-08-22 · mous range of ornamental herbaceous plants....

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Transcript of HO-102 Annual and Perennial Flowers · 2019-08-22 · mous range of ornamental herbaceous plants....